US5118190A - Sagnac-type fiber-optic gyroscope - Google Patents

Sagnac-type fiber-optic gyroscope Download PDF

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Publication number
US5118190A
US5118190A US07/564,754 US56475490A US5118190A US 5118190 A US5118190 A US 5118190A US 56475490 A US56475490 A US 56475490A US 5118190 A US5118190 A US 5118190A
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Prior art keywords
fiber
gates
coupling
optic gyroscope
light source
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Expired - Fee Related
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US07/564,754
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Peter Jurga
Hans Poisel
Gert Trommer
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LFK Lenkflugkoerpersysteme GmbH
Airbus Defence and Space GmbH
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Messerschmitt Bolkow Blohm AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
    • G01C19/58—Turn-sensitive devices without moving masses
    • G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
    • G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
    • G01C19/725—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers using nxn optical couplers, e.g. 3x3 couplers

Definitions

  • a fiber-optic gyroscope of the type having a light source coupled through a directional coupler to a fiber optic coil.
  • Light from the light source is split into two beams which circulate in opposite directions through the fiber optic coil, and the phase of the output signals is analyzed to determine the rate of rotation of the gyroscope.
  • a fiber-optic gyroscope of this type is disclosed in U.S. Pat. No. 4,440,498, in which the directional coupler has six gates arranged in groups of three on both sides of a coupling area.
  • the coupling area in this case may be generated by the pressing or melting of optical fibers disposed next to one another.
  • a light source and two receiver diodes arranged symmetrically on either side of the light source are connected on one side of the directional coupler.
  • a fiber coil consisting of a long optical fiber is connected to the outer gates, the center gate, which is opposite the connection for the light source, remaining free and being connectable, for example, with a monitoring circuit in which fluctuations of the intensity of the light source are determined and are taken into account in the measuring results of the fiber-optic gyroscope.
  • This known fiber-optic gyroscope works as a result of the special development of the directional coupler close to the so-called quadrature point, in which the output signals of the receiver diodes have a sinusoidal dependence on the Sagnac phase so that this fiber-optic gyroscope has maximum sensitivity at low rates of rotation.
  • this object is achieved by using an eight-gate directional coupler having four arms respectively leading to gates on both sides of the coupling area, the power distribution to the four output gates taking place with a specific relative phase shifting between the output signals of the coupler.
  • the operating point of the fiber-optic gyroscope may be placed in the quadrature point.
  • the directional coupler is preferably made of four monomode fibers which rest against one another in the coupling area and are melted on by uniform heating.
  • the resulting coupling area is preferably drawn as a biconical taper.
  • the monomode fibers may also be twisted together in the coupling area.
  • the characteristic of the 4 ⁇ 4 coupler which is essential for the desired method of operation of the fiber-optical gyroscope in or close to the quadrature point, in addition to the power distribution to the four outputs, is a specific relative phase shifting between the output signals of the 4 ⁇ 4 coupler.
  • FIG. 1 is a schematic representation of a fiber-optic gyroscope according to the invention having a 4 ⁇ 4 coupler;
  • FIG. 2 is a more detailed schematic representation of the 4 ⁇ 4 coupler
  • FIG. 3 is a schematic representation of the coupling constant between the individual arms of the coupler shown in FIG. 2;
  • FIG. 4 is a schematic representation of a biconically shaped coupler
  • FIG. 5 is a signal diagram of the output signals of receivers of the fiber-optic gyroscope according to the invention.
  • fiber-optic gyroscope 1 has a 4 ⁇ 4 directional coupler 2 which has four gates on both its sides, T 1 to T 4 and T 5 to T 8 respectively, the assigned arms A 1 to A 4 and A 5 to A 8 of which each lead to a coupling area 3 in which they are connected with one another.
  • a light source L is connected with gate T 1 ; gates T 2 , T 3 , and T 4 are connected to receiver diodes D 2 , D 3 and D 4 .
  • Gates T 6 and T 7 situated on the opposite side are connected with a fiber coil 4 consisting of a long monomode optical fiber 5.
  • Gates T 5 and T 8 remain open or are connected with monitoring circuits by means of which, for example, the intensity of the light source is tested and taken into account in the measuring results.
  • the light source L preferably emits unpolarized light in a wide-band frequency range. In the coupling area 3, this light is uniformly distributed on the two gates T 6 and T 7 with which the two ends of the fiber coil are connected so that the split-up light fractions travel through the fiber coil 4 in opposite directions. After passing through the fiber coil 4, the light, again through gates T 6 and T 7 , enters the directional coupler 2 and interferes in the coupling area 3. The interference signal is guided to the receiving diodes D 2 , D 3 and D 4 from the output signals of which the rate of rotation of the fiber-optic gyroscope is determined.
  • the directional coupler 2 is, for example, produced in such a manner that four monomode optical fibers in the coupling area are twister together and carefully heated so that they melt to one another. During the melting-on, the arrangement is drawn such that the coupling area obtains a biconical shape corresponding to FIG. 4, the thinnest point of which is situated in the center of the coupling area 3. The four optical fibers at both ends of the fused-together coupling area will then form arms A 1 to A 4 and A 5 to A 8 .
  • the 4 ⁇ 4 directional coupler 2 While a known 3 ⁇ 3 directional coupler must be constructed as symmetrically as possible in order to have a high sensitivity for measuring low rates of rotation, for the purpose of which all three coupling constants have the same size and the coupling length is selected such that the energy distribution on the three arms of the directional coupler amounts to one third respectively, the 4 ⁇ 4 directional coupler 2 according to the invention must have an asymmetric power distribution so that the receiving signals do not depend on a pure cosine function of the Sagnac phase.
  • a high sensitivity of the fiber-optic gyroscope 1 for the operation close to the quadrature point, i.e., for the measuring of low rates of rotation, is obtained, for example, for the following products from the coupling length L of the coupling area 3 and the coupling constants K ij :
  • the indices i and j of the coupling constants correspond to the indices of gates T k or arms A k so that, for example, coupling constant K 16 represents the coupling between arms A 1 and A 6 in coupling area 3.
  • the output signals P 1 , P 2 , P 3 and P 4 shown in FIG. 5 are obtained at gates T 1 to T 4 , specifically:
  • the directional coupler has fixed defined phase relations between its output amplitudes and does not just represent a power distributor without any fixed phase relations.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
  • Power Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Gyroscopes (AREA)
US07/564,754 1989-08-09 1990-08-09 Sagnac-type fiber-optic gyroscope Expired - Fee Related US5118190A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3926313A DE3926313A1 (de) 1989-08-09 1989-08-09 Faserkreisel vom sagnac-typ
DE3926313 1989-08-09

Publications (1)

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US5118190A true US5118190A (en) 1992-06-02

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US07/564,754 Expired - Fee Related US5118190A (en) 1989-08-09 1990-08-09 Sagnac-type fiber-optic gyroscope

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US (1) US5118190A (enrdf_load_stackoverflow)
EP (1) EP0412311B1 (enrdf_load_stackoverflow)
DE (2) DE3926313A1 (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5854678A (en) * 1996-06-28 1998-12-29 Honeywell Inc. Three-axis fiber optic gyroscope having a single source and multi-coupler configuration
US20120281990A1 (en) * 2011-05-02 2012-11-08 Massachusetts Institute Of Technology Optical receiver configurable to accommodate a variety of modulation formats
US10830589B2 (en) 2016-07-29 2020-11-10 The Board Of Trustees Of Western Michigan University Magnetic nanoparticle-based gyroscopic sensor
CN116026329A (zh) * 2023-03-31 2023-04-28 中国船舶集团有限公司第七〇七研究所 高可靠性惯性组件及惯导系统

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4301479A1 (de) * 1993-01-21 1994-07-28 Deutsche Aerospace Verfahren und Vorrichtung zum Korrigieren der Meßsignale eines Faserkreisels

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4440498A (en) * 1981-11-13 1984-04-03 The United States Of America As Represented By The Secretary Of The Navy Optical fiber gyroscope with (3×3) directional coupler
US4573797A (en) * 1984-02-24 1986-03-04 The United States Of America As Represented By The Secretary Of The Navy Analog fiber gyro with extended linear range
US4822128A (en) * 1985-10-16 1989-04-18 Hitachi, Ltd. Optical fiber star coupler and method of manufacturing the same

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4445780A (en) * 1982-03-01 1984-05-01 The United States Of America As Represented By The Secretary Of The Navy Fiber optic rotation-sensing gyroscope with (3×2) coupler
US4479715A (en) * 1982-03-09 1984-10-30 Sheem Sang K Optical rotation-sensing interferometer with (3×3)-(2×2) directional coupler
JPS6021706U (ja) * 1983-07-19 1985-02-14 アルプス電気株式会社 スタ−カプラ
US4674881A (en) * 1984-04-25 1987-06-23 Northrop Corporation Open loop thin film laser gyro

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4440498A (en) * 1981-11-13 1984-04-03 The United States Of America As Represented By The Secretary Of The Navy Optical fiber gyroscope with (3×3) directional coupler
US4573797A (en) * 1984-02-24 1986-03-04 The United States Of America As Represented By The Secretary Of The Navy Analog fiber gyro with extended linear range
US4822128A (en) * 1985-10-16 1989-04-18 Hitachi, Ltd. Optical fiber star coupler and method of manufacturing the same

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5854678A (en) * 1996-06-28 1998-12-29 Honeywell Inc. Three-axis fiber optic gyroscope having a single source and multi-coupler configuration
US20120281990A1 (en) * 2011-05-02 2012-11-08 Massachusetts Institute Of Technology Optical receiver configurable to accommodate a variety of modulation formats
US10009115B2 (en) * 2011-05-02 2018-06-26 Massachusetts Institute Of Technology Optical receiver configurable to accommodate a variety of modulation formats
US10830589B2 (en) 2016-07-29 2020-11-10 The Board Of Trustees Of Western Michigan University Magnetic nanoparticle-based gyroscopic sensor
CN116026329A (zh) * 2023-03-31 2023-04-28 中国船舶集团有限公司第七〇七研究所 高可靠性惯性组件及惯导系统
CN116026329B (zh) * 2023-03-31 2023-05-30 中国船舶集团有限公司第七〇七研究所 高可靠性惯性组件及惯导系统

Also Published As

Publication number Publication date
DE3926313A1 (de) 1991-02-14
DE3926313C2 (enrdf_load_stackoverflow) 1993-07-22
EP0412311B1 (de) 1992-05-13
DE59000125D1 (de) 1992-06-17
EP0412311A1 (de) 1991-02-13

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